It’s only when you’re walking down the airport runway that you realize how big it really is. Runways are designed on an inhuman scale. If you’re an aircraft, they’re just long enough to claw yourself into the air. This one, Tempelhof runway 9L/27R, is 2,094 meters long. It takes you 20 minutes of brisk walking to cover the distance a Pan Am Boeing 747 would accelerate through in 60 seconds. This is clearly not a landscape built for feet.

Except, scratch that. You look around and there are people everywhere. Some, like you, are walking down the asphalt. Many more have taken to the grass, occasionally forming sociable huddles around a guitar, or the Berlin equivalent of a picnic basket. It’s four years after Tempelhof closed for the last time and after the last aircraft departed – an Antonov AN-2 delayed by bad weather. Now this is a place being reworked for a different scale of existence. Before, everything needed to be colossal. This place is still vast – 100 acres larger than Manhattan’s Central Park – and in satellite photos it looks like a 400-hectare divot has been whacked out of Berlin by some continent-sized golf club. On the ground, it’s so big that there’s little sense of being in a city park at all. You’re not in Berlin anymore – you’re in Tempelhof.

You’ve been told that the terminal building, once one of the 20 largest buildings in the world, is well worth seeing. From this end of 27R it’s unimposing, a low dark silhouette perhaps a quarter-hour’s stroll away. Half an hour later you still haven’t reached it, and it has eaten the horizon. This 4,000-foot-long semicircle of hallways and hangers was designed to be the ultimate symbol of National Socialism – an eagle, stooping for a kill. Its roof was a mile long. Today the terminal building is a mass of private offices and rental space, and it’s frequently used for events that require a stage of epic proportions.

%Gallery-184233%Someone once said that Tempelhof airport united “the characteristics of an inland sea with the yearning for faraway places.” The only thing you’re yearning for right now is a cold beer, but the contents of your water bottle will have to do. You sit on the runway’s grass verge and watch everyone else. Most of them are clearly smarter than you, because they brought wheels: rollerblades, bicycles, skateboards and Segways. The runways funnel the speedy, and everyone else is meandering, enjoying a succession of moments. Nobody is hurrying because there’s no point – everywhere here is too far away to arrive quickly. You start to realize what you’ve been missing. It’s not just about geography – it’s also about time.

In a city famous for never standing still, this park (its official name: Tempelhof Freedom) is evolving into something much busier. Great strips of it are being put aside for formal development, while others are being used in more organic ways, the most charming being the allotment shantytown of Stadtteilgarten Schillerkiez. Here, wooden benches, pallets, boxes and barrels have been bolted together to form something excitingly ramshackle – a dab of Harry Potter, a sprinkle of Deadwood – and every hollow is filled with soil and sprouting plants (digging is forbidden, so this is the only way crops can be grown). Nearby, poles hoist animal sculptures into the air at the edge of grassland where dogs must be kept on a leash because the wildlife, including several red-listed species, is making a comeback. It looks like anyone could turn up and make something – a community art-space that would never run out of room. However, it might run out of time.

In four years, this park will be transformed for Germany’s International Horticultural Fair, creating an entirely new landscape specifically designed for foot traffic. Developers Gross Max and Sutherland Hussey will be improving access and installing pathways galore, although their redesign proposal affirmed a commitment to retaining “a contemporary prairie for the urban cowboy.” The same plan called for a 200-foot-high hill capped with an angel – not the first time a local architect has suggest Tempelhof has its own mountain. Other developments will include the relocation of the Central and Regional Library for Berlin to the park’s southwest edge – a wise move judging from the amount of people currently sat enjoying the afternoon sunlight with a book in their hands. The park will fill up, inside and out, and as the official redevelopment website notes, “the open spaces of Tempelhof Freiheit will not remain the way they appear today.”

You walk until your feet hurt, and you still get nowhere. So you turn around, and make your way back to the shallows, up the slope to the park gates at Oderstrasse (opened at 6 a.m.; closed at sunset). This late in the day everyone is reluctantly heading back towards reality, lingering on the grass to watch the sun redden and slip behind the apartment blocks in the far distance, at the other side of the world. Everything is in the pastel evening shades of England’s Dartmoor or the hills of Yorkshire. A wild place, uncolonized but belonging to anyone who wants it. How will it look the next time you visit? You’re glad you saw it now, before it all changed once again. And now you need that beer.